Electric induction apparatus



March 13, 1951 F. R. D'ENTRl-:MONT

ELECTRIC INDUCTION APPARATUS 2 Sheets-Sheet 1 Original Filed April 27, 1946 HHH-Nmlm Inventor: pranklin D. D'Entremontj,

)Il a lllllflllllllllllIIIIIQVIIIIIIIIIII "hull l-l i s Attorney.

March 13, 1951 F, R, D'ENTREMONT 2,544,658

ELECTRIC INDUCTION APPARATUS original Filed April 27, 194e zsheeis-sheet 2 Inventoriranklin F2. Dllntremont,

L-lis Atorney.

Patented Mar. 13, 1951 ELECTRIC INDUCTION APPARATUS Franklin R. DEntremont, Lynneld, Mass., assignor to General Electric Company, a corporation of New York lOriginal application April 27, 1946, Serial No. 665,423. Divided and this application October 16, 1947, Serial No. '780,129

Claims.

This is a division of my application, Serial No. 665,423, for electric induction apparatus, filed April 27, 1946, now Patent No. 2,482,403, and assigned to the same assignee.

The invention relates to electric induction apparatus and more particularly to improvements in current transformers. Certain features of the apparatus described herein relating to an inductive apparatus of particular construction which is not dependent upon the specific winding spool construction which is included in the claims herein constitutesthe subject matter of my divisional application Serial No. 67,262 filed December 27, 1948 and assigned to the same as.

taken on the line I-I of Fig. 2; Fig. 2 is a planl view of the current transformer partly in section; Fig. 3 is a transverse midsectional view of the transformer shown in Figs. 1 and 2; Fig. 4 is a detailed, partly broken away, perspective view of certain internal structural features of the transformer; Fig. 5 is a perspective view of the completed core and coil assembly of the transformer mounted on its base; Fig. 6 is a partly broken away perspective view showing details of the core'and its insulation; Fig. 7 is a view, partly in section, of the secondary terminal board and cover construction With the cover in the operating position; and Fig. 8 is similar to Fig. 7 but showsv the cover in its reversed or shipping position.

Referring now to the drawing, more particularly to Figs. l, 2, 3, and 5, the transformer consists essentially of a magnetic core I, a primary winding 2, and a secondary winding comprising a pair of coils 3 and 4.

The primary winding is of large current carrying cross section andis shown as comprising two strip conductors v5 and 6. As shown most clearly in Figs. 2 and 5, the primary winding 2 has a generally S-shaped configuration. As it only passes through the'windowof the core I once, it is a one-turn winding. It is provided 2 with heavy terminals 'I and 8 which are preferably of duplicate construction and may consist generally of heavy copper pieces which are bent at right angles to an L-shape.

.In order to reduce the overall length of the primary winding so as to be able to put as high a current carrying capacity primary winding as possible into a given size casing, a novel construction is employed. This consists of making the strands or strips 5 and 6 with unequal length ends. For example, as shown in Fig. 2, the lefthand end of strand 5, which is on the outside, is

shorter than the end of strand 6, which is on 'the inside. The strands themselves are preferably of duplicate construction so that at the right-hand end the strand 6, which will be on the outside, will be shorter at the end than the strand 5, which at that end is on the inside. This can be seen from Fig. 1 which shows that in the center plane dened by the line l-I in Fig. 2, the strand 6 ends, while the strand 5 continues on away fromthe observer. Conversely, at the left-hand end of the primary Winding as shown in Fig. l, the end of the strand 5 is shown while the strand 6 continues on toward the observer. In order that the duplicate strands will iitv closely together, itis necessary that the reverse bend of each strand at its shorter end be wider than at its longer end because the bend having the longer end of each strand fits inside the bend having the shorter end. The normally vvertical portions of the two terminals are milled out on one side of their vertical center line to a. depth equal substantially to the thickness of one of the strands. In other words, the contacting surfaces of the terminals have a stepped configuration which is complementary to the stepped configuration of the ends of the primary Winding. The complementary surfaces are fitted together and are preferably permanently attached to each other such as by brazing, and it will be seen from Figs. l and 2 that due to the fitting together of these stepped surfaces, the overall length between the ends of the terminals 'I and 8 is reduced by the overall thickness of the primary conductor in comparison with a conventional terminal connection in which the two strands would be of equal length and a fiat terminal surface would be brazed to the outer surface of the outer strand.

The primary winding and the connections to its terminals are insulated in any well known manner such as by means of insulating tape 6 which is wrapped around them.

vThe secondary coils 3 and 4 are preferably 3 duplicates and they are wound on insulating spools le which also are preferably duplicates. As shown most clearly in Fig. 4, each winding spool I consists of duplicate channel-shaped pieces of solid insulation such as pressboard. These pieces may be molded from rectangular sheets of pressboard and they are characterized by having outwardly extending anged ends I2 on their center portion and straight projections I3 at the ends of their sides. The spools are formed by placing the channel-shaped members face to face with their sides in overlapping relation. In this way the same size parts can together form spools of a wide variety of diierent sizes by varying the amount of overlap so that the spool can be adapted to nt on different size cores.

The spools are placed on the core in such a way v that two of the ilanges or opposite ends extend along the inside of the yoke portions of the core for the purpose of insulating the secondary coils from the yoke portions of the core. At the same time, the straight extensions i3 on the spools which are at the sides of the core serve to insulate the secondary leads from the core.

rihe core I the details or" which are shown most clearly in Fig. 6, consists of two U-shaped members I4 and I5, each of which consists of a like number of flatwise bent strips of magnetic material. The details of how this core is formed are not part of the present invention and one suitable way of making the core forms the subject matter of application Serial No. 553,523 (now Patent No. 2,477,350), led September 11, 1944, in the name of G. G. Somerville, and assigned to the assignee of this application. Briefly, this method is characterized by cutting the lamination p-ieces to the desired length on an index shearing machine which, at the same time, provides at least one perforation in each piece. These perforations, `which are known as locating holes, serve to align the pieces, and by reason of the on center position of this locating hole relative to the ends of the pieces, combined with alternate end for end reversal of adjacentI pieces, a staggered or overlapping butt joint construction, such as is shown in Fig. 6, may be obtained. AS shown in Fig. 6, the locating holesl are in the yoke portions of the core and I make further use of one of these locating holes for the purpose of mounting a set of compensating windings on the core. To that end, an insulating tube I6 is inserted in one of the aligned sets of locating holes in the core.

The compensating windings are most clearly shown in Fig. 5, one being a multi-turn winding Il having leads I8, and the other being a short circuiting-turn winding I9. The leads I8 of the compensating winding I1 are connected respectively to a lead 20 on secondary coil 3 and a lead 2| on the secondary coil 4. This type of compensation is described and claimed in Patent 1,722,167, granted July 23, 1929, in the name of Myron S. Wilson, and assigned to the assignee of this application.

The leads I8, 20, and 2| and their interconnections are relatively uninsulated and the primary insulation between 'them and the core is obtained by solid insulation which is applied to the core and which cooperates with the ends of the spools I for the secondary winding coils. This additional solid insulation consists primarily of a rectangular piece ofinsulating material 22, such as press-board, which is placed under the upper yoke portion of the core and which is bent around so as to follow part'way down the upper portions of the inside of the core legs. Holding this in place is another piece of solid insulation 23 which is placed on top of the core and has an opening registering with the tube I6. The sides of the piece 23 are folded down along the sides of the upper yoke part of the core and these sides have tabs 24 which are then folded under and into the core window ior holding the piece 22 in place. The lower outside ends of the sides of the piece 23 overlap the straight projections I3 of the winding spools IU and as shown most clearly in Fig. 5, they are tted between the core and these straight projections I3. In this manner the core I3 is fully insulated from the secondary coils and their leads, and also from the compensating windings Il and I9 and from the leads I8 0f the compensating winding I l.

The transformer is mounted on a base 25 by means of a bracket 26 which is shown as a receptacle-like member, the bottom of which rests on the base 25 and is preferably permanently attached thereto, such as by welding. The bottom yoke of the core I is seated in the bracket 26 and is held rmly in place by means oi' a binding strip 2l which is placed against the top and sides of the core underneath the insulating piece 23. This binding strip has ends 28 which are securely attached to the upturned ends oi the bracket preferably by projection welding, as shown by the two spots 29 at each end. Before the transformer is encased, insulating barriers 3i) in the form of curved solid insulating pieces are inserted between the secondary coils and the primary winding, as shown in Fig. 1.

The transformer case consists of two main parts 3| and 32 which are preferably of duplicate concave construction. They may be molded from solid organic insulating material which has been impregnated with a hardened synthetic resin. They are attached at the bottom to the sides of the bracket 26 by means of screws 33 which are threaded in to openings 34 provided l or that purpose in the sides of the bracket 25. The space between the duplicate concave casing parts 3| and 32 is occupied by a center band 35 which is shown most clearly in Fig. 3 and which is seated in grooves provided for that purpose in the facing edges of the parts 3| and 32. The upper ends of the casing paris 3| and 32 are held together firmly by means of metal strips 36 whose ends are bent over at 31 and 3B for that purpose. These strips 36 serve an additional purpose and that is to complete the connections for the secondary winding. Thus, the bent-over perdons 3l are connected to the remaining terminals of the coils 3 and 4 which come out of the coils 3 and 4 on the opposite side from the side where their leads 20 and 2I come out.

The bent-over portions 38 end in binding posts 39 by which external connections to the secondary winding are made. As will be seen most clearly from Fig. 3, these bent-over ends 38 and the binding posts are in a recess in the top edge of the casing parts 32. Strip conductors 4Q, as shown in Fig. 7, are connected to each binding post and attached to one of these strip conductors is a pivoted strip or link 4| which is for the purpose of short-circuiting the secondary windin-l so as to permit connection of the primary winding in a current carrying circuit at such times as there is no external circuit connected to the secondary winding. The bent-over ends 38 oi the conducting strips 36, the binding posts 39, the conducting strips 40 and the pivoted link 4I, together vconstitute a terminal board for the sec- 5 ohdary winding of the transformer and this terminal board is enclosed by a cover 42 which is reversible and which has openings 43 in one edge thereof for allowing external conductors to make connection with the binding posts 39. The cover has an integral projection 44 which, when the cover is put on in such a way that the openings 43 are in alignment with the binding post openings, will occupy the space which the pivoted link 4I would occupy if it were in its bridging kor interconnecting position for completing a connection between the two binding posts. In other words, the projection 44 prevents the cover being put in place when the secondary winding is shortcircuited for the pivoted link. As shown most clearly in Fig. 8, the cover 4I also has another inner projection 45 which when the cover is put on in its reversed position, will occupy the space which would be occupied by the pivoted link 4| if it were in its open position. In other words, the projection 45 prevents the cover being put on in its closed or shipping position except when the pivoted link is in its short-circuiting position.

The cover 40 is held in place in either position by any suitable means, such as a knurled nut 46 threaded into a screw 41, which is attached to the casing part 33.

The recess in the duplicate casing part 3l corresponding to that in which the terminalboard is located in part 32 ispreferably closed by a suitable cover member 48 which may carry a name plate if desired. The free spaces in the casing are lled with suitable insulating compound (not shown).

While there has been shown and described a particular embodiment of this invention, it will be obvious to those skilled in the art that Various changes and modifications can be made therein without departing from the invention and therefore it is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention:

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A Winding spool comprising, in combination, two channel-shaped insulating members placed face to face with their sides in overlapping relation, the ends of the center portions of said channel-shaped members being anged outwardly, the ends of the side portions of said members being straight and extending beyond said flanged ends.

2. A half spool for a conductive winding comprising, in combination, a channel-shaped piece of insulating material, outwardly bent integral flanges at the center of both ends of said channel, and straight projections beyond said flanges on the sides of said channel.

3. Electric induction apparatus comprising, in combination, a magnetic core having at least one winding leg portion and one yoke portion, an insulating spool on said winding leg portion, said spool having outwardly extending anges on two opposite sides of at least one end thereof, the

6 flange on one of said sides extending along the inner surface of said core yoke portion, said spool having straight projections on the other opposite sides the said end thereof, and solid insulation surrounding said core yoke portion, said solid insulation and said straight projections on said spool being in overlapping relation, said spool comprising two channel-shaped members embracing opposite sides of said winding leg with the side parts of said channel-shaped members in overlapping relation.

4. Electric induction apparatus comprising, in combination, a two-legged magnetic core with yoke portions joining the ends of its legs, separate insulating spools on said legs, said spools having outwardly extending flanges on two opposite sides of both ends, the flanges on one of said sides extending along the inner surfaces of the core yoke portions, said spools having straight projections on two other opposite sides at both ends, and solid insulation surrounding one of said core yoke portions, said solid insulation and said straight projections on said spools being in overlapping relation, said spools each comprising two similar shaped channel members embracing opposite sides of their respective winding legs and with their side parts in overlapping relation.

5. Electric induction apparatus comprising, in combination, a generally rectangular magnetic core of rectangular cross section having a Winding leg and a yoke portion, a conductive coil on said winding leg having a plurality of leads, and means for insulating said coil from said core comprising a spool of insulating material having a main body of rectangular cross section interposed between said core Winding leg and said coil, integral outwardly extending flanges on the ends of said main body for insulating the ends oi said coil from said core yoke portion, and integral straight projecting portions on said main body adjacent to and extending beyond said flanges for insulating said leads from said core, said spool comprising two substantially identical square edged channel-shaped members the ends of whose center parts are turned outwardly to lform said outwardly extending `iianges and the ends of Whose side parts extend straight to form said straight projecting portions.

FRANKLIN R. DENTREMONT.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,517,770 Ziegler Dec. 2, 1924 1,720,943 Chapman July 16, 1929 1,880,809 Clarke Oct. 4, 1932 2,235,425 Franz Mar. 18, 1941 2,246,167 DEntremont June 17, 1941 2,339,432 Stahl Jan. 18, 1944 2,349,782 Wethmuller May 23, 1944 2,380,203 Tognola July 10, 1945 

